The present disclosure relates to the technical field of a semiconductor device, and a manufacturing method of a semiconductor device. In detail, the present disclosure relates to the technical field of a semiconductor device having a so-called flip-chip structure, in which a second semiconductor chip is bump bonded on a first semiconductor chip, and a manufacturing method of this semiconductor device, which forms a fillet with a suitable width while preventing a reduction in the degree of freedom in design.
A semiconductor device with a flip chip structure (chip-on-chip type) is known which bump bonds another semiconductor chip on a semiconductor chip.
FIGS. 10A and 10B schematically show a structure of a semiconductor device with a flip-chip structure.
As shown in the perspective view of FIG. 10A and the cross-section view of FIG. 10B, a semiconductor device with a flip-chip structure has an upper chip 102 bonded on a lower chip 101, via a plurality of bumps 103.
The upper chip 102, as a memory chip (for example, a DRAM (Dynamic Random Access Memory) or the like), bump bonded on the lower chip 101, as a logic circuit chip, can be included as an example of such a semiconductor device with a flip-chip structure.
In a semiconductor device with a flip-chip structure, filling of a liquid resin, called an under-fill material (a UF material) for the purpose of protecting the bumps 103, is performed between the chips bonded via the bumps 103, and sealing is performed for the clearance between the lower chip 101 and the upper chip 102.
FIG. 11 shows a state in which resin 104 is filled as an under-fill material.
As shown in FIG. 11, the resin 104 is injected at a prescribed position of the lower chip 101, by a nozzle 110. This injected resin 104 leaks out and spreads on the lower chip 101, and reaches within the bonding region with the upper chip 102. The resin 104 penetrates the spaces between the bumps 103 (spaces between bumps) by a capillary phenomenon, and the clearance between the lower chip 101 and the upper chip 102 is sealed.
In this case, in order to prevent leakage of the resin 104 to the outside of the lower chip 101, a dam 101a with a prescribed height is included at an outer peripheral section of the lower chip 101 (refer to FIG. 10B and FIG. 11).
The resin 104 which seals the clearance between the lower chip 101 and the upper chip 102 as described above is cured, for example, by heat treatment or the like. In this way, cracking of the bumps 103 due to stress concentrations is prevented, and the connection reliability between the lower chip 101 and the upper chip 102 (also including the electrical connection via the bumps 103) can be improved, by relaxing the influence of external stresses such as moisture absorption.
Here, after the resin 104 is injected as a UF material such as described above, the resin 104, which has advanced into the spaces between the bumps by a capillary phenomenon, will also leak out to the outside of the bonding region of the lower chip 101 and the upper chip 102. In this way, a fillet 105 is formed, such as shown in the following FIG. 12.
In FIG. 12, a state of a semiconductor device after the injection of resin 104 is shown by an upper view, and a circle P within the figure represents the injection point of the resin 104. In accordance with the injection of the resin 104 by the tip of the nozzle 110, the resin 104 advances from the injection position P in the direction of the bonding region with the upper chip 102. Then, after the spaces between the bumps within the bonding region are filled such as described previously, the resin will leak out to the outside of the bonding region.
The fillet 105 indicates the resin portion formed outside of the bonding region with the upper chip 102.
Here, in a semiconductor device with a flip-chip structure, such as shown in the upper view of FIG. 13, a plurality of lines of wiring 101b is formed on the surface side of the lower chip 101, that is, on the bonding surface side with the upper chip 102.
In accordance with the formation of these lines of wiring 101b, concave and convex sections are formed on the surface of the lower chip 101, by the formed portions/un-formed portions of the wiring 101b. 
In the case where such concave and convex sections are formed on the surface of the lower chip 101 in accordance with the formation of the wiring 101b, it becomes difficult to form the fillet 105 with a prescribed width.
The reason for this will be described by with reference to FIGS. 14A and 14B. In FIGS. 14A and 14B, a case is illustrated where the advancing direction of the resin 104 and the wiring direction are parallel to each other. That is, in this case, the resin 104 is injected from the injection position shown by the thick arrow in FIG. 14A, and in this way, the resin 104 advances from the injection position in the direction in which the upper chip 102 is formed, and the advancing direction of the resin 104 becomes a direction parallel to the wiring direction of the wiring 101b. 
In this case, when the resin 104 is injected such as in FIG. 14A, a width of the fillet 105 is not able be formed with a prescribed width, such as shown in FIG. 14B (a width shown by the dotted line within the figure).
In the case where there are concave and convex sections on the lower chip 101 in accordance with the wiring 101b, the resin 104 injected to the lower chip 101 penetrates within the bonding region with the upper chip 102 by a capillary phenomenon, and thereafter remains in these convex sections, due to surface tension finally acting on the convex sections as formed portions of the wiring 101b. In other words, it may not be possible to go ahead of any of the lines of wiring 101b. Accordingly, the spreading of the fillet 105 will be stopped by the formed portions of the wiring 101b, and the formation of the fillet 105 with a prescribed width becomes difficult.
Note that, when stating for confirmation, if the injected resin 104 reaches within the bonding region with the upper chip 102, it will advance within the bonding region by a capillary phenomenon due to the spaces between the bumps within the bonding region. However, outside of the bonding region, a capillary phenomenon does not occur, the advancement of the resin is stopped by the formed portions of the wiring 101b at the side surface section of the bonding region, and the width of the fillet 105 will be restricted by the formed positions of the wiring 101b. 
On the other hand, in the back side of this bonding region (the back side when viewed from the injection position), since the convex sections, which obstruct the advancement of the resin 104 by a capillary phenomenon (the convex sections orthogonal to the resin advancing direction), do not exist in the bonding region, the spreading of the fillet 105 will not be restricted.
As a result of this, as the fillet 105 of this case, the spreading of this side surface section, when viewed from the injection position of the resin 104, will be restricted, such as shown in FIG. 14B.
It is desirable that the width of the fillet 105 is formed with a prescribed width, in terms of the reliability, quality and the like of bonding. Therefore, it may be necessary to avoid situations such as when the fillet width is restricted, such as described above.
Here, for example, such as described in JP 2010-192886A, the inventors have proposed technology, related to a semiconductor device with a flip-chip structure in which concave and convex sections are provided on the surface of the lower chip 101 in accordance with the formation of the wiring 101b, which forms slits for the wiring 101b. 
FIGS. 15A and 15B are explanatory diagrams for a semiconductor device in which slits are formed. FIG. 15A is an upper view of the semiconductor device, and FIG. 15B is a cross-section view of the semiconductor device (only the formed portions of the slits are extracted).
As shown in FIG. 15A and FIG. 15B, in a semiconductor device of this case, slits 106 are formed, as concave sections, on the wiring 101b formed in a surrounding section of the bonding region with the upper chip 102.
By forming such slits 106 on the surrounding section of the bonding region with the upper chip 102, the resin 104, which has advanced within the bonding region by a capillary phenomenon, can be poured into an outer side, via the slits 106. That is, the width of the fillet 105 can be prevented from being restricted by the formed portions of the wiring 101b. 
By an adjustment of the length of these slits 106, it becomes possible for an adjustment of the width of the fillet 105, and it becomes possible for a formation of the fillet 105 with a prescribed width.